Method for producing reinforced sponge



METHOD FOR PRODUCING REINFORCED SPONGE Application August 13, 1956, Serial No. 603,572

Claims priority, application Germany August 30, 1955 4 Claims. (Cl. 18-59) This invention relates generally to a method of producing viscose sponges used for cleaning purposes and more specifically to a method of producing a viscose sponge having a reinforced outer surface.

Scrubber-like appliances of sponge material have recently been developed for cleaning purposes. When adapted to floor-cleaning, this sponge material has been cut into rectangular blocks, thereby forming a rubbing surface, and fixed in a clamp. The clamp is provided with a handle in order to expedite manipulation thereof. During cleaning operations the sponge is repeatedly squeezed, by forcingthe same between two pressure rollers, by pressing the same against an apertured plate, or by other means. Thus it is seen that the sponge block is recurrently subjected to high stresses, especially in the region of the side edges thereof, damaging the same to the extent that an early replacement is required unless the composition of the sponge material is such that it Will withstand these stresses.

Sponges made from regenerated cellulose, such as viscose, have proved to be particularly suitable for use as cleaning appliances, but it has been found that sponges of this type have the disadvantage of not being sufficiently resistant to stresses such as those produced by the aforementioned squeezing operations to warrant commercial success.

It is therefore an important object of this invention to provide a viscose sponge with a layer of reinforcing material which is both flexible and yielding and which will strengthen the outer surface rendering the sponge resistant to wear and stresses usually encountered when subjecting the same to wringing rollers.

It is another object of this invention to provide a viscose sponge having a very tough and Wear-resistant outer skin.

A further object of this invention is to provide a viscose sponge having a stress-resistant outer surface useful over prolonged periods of scrubbing and wringing operations.

In accordance with the present invention a seamless sheath of knitted fabric is embedded in the outer surface of a paste material of the type generally used in the production of sponges. Upon subsequent regeneration or decomposition of the paste material the fabric becomes intimately bonded to the sponge, rendering the outer surface thereof tough and stress-resistant.

Other objects and advantages of the present invention will be apparent from the following detailed description when considered in conjunction with the accompanying drawings, wherein Figure 1 is an elevational view, partly in section, showing the sponge material discharge tube and the fabric sheath drawn thereover,

Figure 2 is a view similar to that shown in Figure 1 but showing the sponge mold telescoped over the sheath and tube in position to receive the pasty sponge material which is shown entering the tube,

Figure 3 shows the mold and sheath in section filled with the sponge material and forced outwardly by the nited States Patent@ ,m 2,913,77 Patented Nov. 1959 pressure thereof approximately to the position of removal from the tube, and

Figure 4 shows in perspective the regenerated sponge cut into the desired shape for use as a cleaning appliance.

In the preferred embodiment of this invention a sponge material of known composition is supplied under pressure through an extrusion tube indicated at 10. A control valve 11 of any known construction is mounted in the tube so that flow of the sponge material may be regulated. The outlet end portion of tube 10 is enlarged at 12. and has dimensions similar to but slightly less than, those of the mold indicated at 13. An open mesh, seamless, knitted fabric sheath 14-, resiliently stitched at one end, is drawn over the outlet end 12 of the tube in the manner shown by Figure 1. It is important that the fabric have a relatively coarse mesh so that the extruded sponge material may pass readily therethrough and enclose the fibers of the sheath, thereby effecting an intimate bonding therebetween. Next, the sponge mold 13 is telescoped over the fabric covered sheath in the manner shown by Figure 2', and control valve 11 is opened.

Inasmuch as the sponge material is discharged under pressure, a slight counter pressure should be applied to the mold 13 in order to control the filling thereof. As

the mold fills, it is forced outwardly of the tube 10 and against. the counter pressure until it is completely filled. The pressure on the sponge material forces the sheath firmly against the inside wall of the mold. Obviously the magnitude of counter pressure may be varied depending on the density of the material filling the mold.

Subsequent to filling, the sponge molds are immersed in a shallow vat containing an aqueous solution of sodium sulfate wherein regeneration occurs. Thereafter, the sponge block is removed from the mold, Washed and cut into the desired shape, shown by way of example at 16 in Figure 4. Finally the blocks are bleached, aftertreated and finished. The cut areas represent the rubbing surface used for cleaning purposes.

Example In one specific example of this invention the sponge paste or material used consisted of 22.1% viscose, 77.2% crystallized Glaubers salt having grain diameters up to 5 mm. and 0.7% cotton combings of from 10 to 15 mm. in length, this paste being prepared in a pulper. The viscose used contained 8.6% celluose, 6.1% NaOH, and 3.5% sulphur, had a viscosity of 1000 and an NH Cl number of 20.

The aforementioned paste was deposited into a sheathlined mold 44.5 cm. in width, 12.5 cm. in depth and cm. in length and the corresponding dimensions of the sheath, in an untensioned state, were 44 by 12 by cm. The yarn used for the cotton sheath had the metric num ber 72/2 ply, the mesh density was ZO/inch, and the total weight of the sheath was 22 grams. The sponge material was deposited under a pressure of four atmospheres and the filling process terminated after approximately one minute.

Subsequent to filling, the mold and the paste contained therein was immersed in a shallow vat containing an aqueous bath with 290 grams per liter of sodium sulphate maintained at a temperature of 95 C., although it should be understood that the bath could contain from 260 to 320 grams per liter of sodium sulphate and that the temperature range of 95-100 C. is satisfactory.

After approximately three and one half hours of immersion in the bath, decomposition of the paste material was completed. The sponge block was then removed from the mold and exposed to a rinse of 75 minutes duration for the purpose of removing the salt contained therein. Thereafter the sponge block was cut into desired shape, after which the sections were bleached in a 0 bath containing one gram per liter of chlorine, aftertreated in a solution containing two grams per liter hydrochloric acid and rinsed, followed by impregnation and passage through a finish.

In order to give the finished sponge even further reinforcement, an additional coating of viscose may be brushed thereon or applied in any other manner after removal of the sponge from the mold. Moreover, the mold may be coated with a reinforcing layer of viscose before telescoping the same over the sheath covered, enlarged portion of the tube, and may be of any desired shape or size. Additionally, it is within the scope of this invention to line the mold with the fabric sheath before either is drawn over the tube.

What is claimed is:

1. The method of producing reinforced sponge comprising the steps of drawing a coarse-mesh fabric sheath over the open end of a tube, telescoping a hollow mold over the sheath, forcing a sponge material through the open end of the tube into the mold and through the coarse-mesh fabric sheath, and aftertreating the material to regenerate the same and to bond the sponge material to the fabric.

2. The method of producing reinforced viscose sponge comprising the steps of drawing a coarse-mesh knitted fabric sheath longitudinally over the open end of an extrusion tube, telescoping a mold over the tube and sheath, extruding a sponge paste under pressure through the open end of the tube into the mold and through the coarsemesh sheath thereby filling the mold and forcing the same off the tube, aftertreating the paste to regenerate the viscose and to dissolve the pore forming substance contained therein, removing the regenerated sponge from the mold and finally washing, drying and cutting the same into desired shape.

3. The method of producing block-shaped reinforced viscose sponges to be used for cleaning purposes comprising the steps of drawing a seamless sheath of coarsemesh knitted fabric, which is resiliently stitched at one end, over the open end of a tubular extrusion tube, telescoping a sponge mold over the sheath and tube, extruding a pasty mass consisting of 22.1% viscose, 77.2% crystallized Glaubers salt and 0.7% cotton combings under a pressure of approximately four atmospheres from the tube into the mold and through the sheath thereby forcing the mold and sheath off the tube, aftertreating the mass in a sodium sulphate solution, removing the sponge blocks from the mold, washing and drying the same and finally cutting the sponge into desired shaped blocks.

4. The method of producing reinforced viscose sponge comprising the steps of lining a hollow mold with a coarse-mesh fabric, telescoping the lined mold over an open end of an extrusion tube while maintaining the fabric positioned within the mold, extruding sponge material under pressure from said tube into the lined mold and through the coarse-mesh fabric, and aftertreating the material to regenerate the same and to bond the sponge material to the fabric.

References Cited in the file of this patent UNITED STATES PATENTS 2,280,022 Banigan et al. Apr. 14, 1942 2,506,249 Tammen May 2, 1950 2,512,506 Saint-Denis June 20, 1950 2,540,906 Overton et al Feb. 6, 1951 2,727,278 Thompson Dec. 20, 1955 2,785,440 Toulmin, Jr. Mar. 19, 1957 FOREIGN PATENTS 384,668 Great Britain Dec. 5, 1932 415,728 Great Britain Sept. 3, 1934 

